Interstitial Lung Disease
Inflammation and progressive fibrosis thicken and stiffen the interstitium between the alveolus and its capillary, so the lung becomes small and stiff rather than obstructed, impairing oxygen diffusion out of proportion to airflow and producing the restrictive, breathless, dry-cough picture that distinguishes it from obstructive airway disease.
In a nutshell
Inflammation and fibrosis thicken the alveolar-capillary interstitium, impairing oxygen diffusion and stiffening the lung, producing restrictive physiology rather than airflow obstruction. Exertional desaturation and fine Velcro crackles are early, sensitive signs. Because fibrosis is largely irreversible, management prioritises removing any identifiable trigger and slowing further decline over reversing existing scar.
Classic presentation
Progressive exertional breathlessness and a dry cough over months to years, with fine bibasal end-inspiratory crackles and sometimes finger clubbing.
Key points
- The pathology is in the interstitium (the diffusion membrane), not the airway, so spirometry shows a restrictive, not obstructive, pattern.
Educational content pending clinical review. Not medical advice.